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Exploring the beautiful nature of California
California Nature: Dolphin
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Related to dolphins and whales, the porpoise
is often referred to as a "small dolphin." The word porpoise has
often been used colloquially to describe porpoises, dolphins and
in some cases larger whales. However, the family of porpoise are
very different from dolphins.
The vast similarities between dolphins and porpoises are
astounding, to the naked and untrained eye, most common people
would be unable to distinguish one from the other; this is
generally because they are related. Porpoises are divided in to
six species and sub species, while dolphins are divided into 40
different main types.
The average dolphin is generally longer than the average
porpoise, and the most obvious visible difference between the
two groups is that porpoises have flattened, spade-shaped teeth.
Porpoise also have small flippers, lack the prominent beak
associated with many dolphins and have a more triangular dorsal
fin rather than falcate.
Dolphin and porpoise may have some key
differences, such as their size, varying types and aesthetic
differences, but regardless of this they share the common
ability to amaze and entrain countless millions who are dazzled
by their amazing intellect and even human characteristics. |
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Dolphins are among the smallest of cetaceans:
whales, dolphins and porpoises. The greatest
number of dolphin species belongs to the largest
cetacean family, the Delphinidae that contain
dolphins widely referred to as ocean
dolphins. Many species of dolphins are
streamlined in shape and have a prominent dorsal
fin, are capable of great speed in the water and
exhibit spectacular acrobatics.
There are some species of dolphin that lack a
dorsal fin but the majority have a dorsal fin
and it is situated midway down the back. Most
species of dolphin have a head that tapers into
a distinct beak with varying numbers of conical,
sharp teeth in both the upper and lower jaw with
some exceptions.
It is difficult to estimate population numbers
since there are many different species spanning
a large geographic area. Dolphins are well known
for their agility and playful behavior, making
them a favorite of wildlife watchers. Many
species will leap out of the water, spy-hop
(rise vertically out of the water to view their
surroundings) and follow ships, often
synchronizing their movements with one another.
Scientists believe that dolphins conserve energy
by swimming alongside ships, a practice known as
bow-riding.
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Dolphins breathe air at the surface of the water through a
single blowhole located near the top of the head. They need to
breathe about every two minutes, but can hold their breath for
several minutes. Their blow is a single, explosive cloud.
Dolphins live in social groups of five to several hundred. They
use echolocation to find prey and often hunt together by
surrounding a school of fish, trapping them and taking turns
swimming through the school and catching fish. Dolphins will
also follow seabirds, other whales and fishing boats to feed
opportunistically on the fish they scare up or discard.
Dolphins are often heard clicking. Contrary to popular thought,
clicking is likely not communication, but rather the sonar
system dolphins use for navigation, food-finding and avoidance
of predators. Clicks are one of three classes of sounds dolphins
produce, in addition to squawks (whose purpose is unknown,
although these sounds are made while dolphins are socializing),
and pure tones, one of which is known as that dolphin's
"signature whistle."
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Dolphins are among the most sexual of animals,
and are not monogamous. When aroused, a dolphin
male may mate several times an hour, often with
the same female but not always. Even
though, males swim away and female dolphins
usually depend on their pods to help
them protect the baby dolphin.
After eleven or twelve months, depending on the
species, a pregnant dolphin gives birth.
Dolphins are among the few animals that have
assisted births; when a dolphin is giving birth,
she’s often assisted by another female dolphin
who acts as midwife.
Birth, can happen anywhere. When it does happen,
the mother’s pod will surround her protectively
while she’s in labor, waiting to fend off any
predators who may be thinking about a quick and
easy meal. Baby dolphins are born tail-first to
avoid get drown and are usually single births,
with the exception of a few smaller dolphin
species which tend to have two calves. Dolphin
mothers help their calves to reach the surface
by swimming beneath them and gently lifting
upward to get their first breath.
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Dolphins have been declared the world’s second most intelligent creatures after
humans, with scientists suggesting they are so bright that they should be
treated as “non-human persons”. Studies into dolphin behavior have highlighted how similar their communications
are to those of humans and that they are brighter than chimpanzees. These have
been backed up by anatomical research showing that dolphin brains have many key
features associated with high intelligence.
The researchers argue that their work shows it is morally unacceptable to keep
such intelligent animals in amusement parks or to kill them for food or by
accident when fishing. Some 300,000 whales, dolphins and porpoises die in this
way each year.“
Many dolphin brains are larger than our own and second in mass only to the
human brain when corrected for body size,” said Lori Marino, a zoologist at
Emory University in Atlanta, Georgia, who has used magnetic resonance imaging
scans to map the brains of dolphin species and compare them with those of
primates.
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